Electric furnace.



No. 721,703. l PATENTED MAR. 3, 1903.

P. L. T. HBROULT.

ELECTRIC IURNAGE.

APPLICATION FILED O43T.11| 1900.

N0 MODEL.

FIG. 2.

UNITED STATES PATENT OFFICE.

PAUL LOUIS TOUSSAINT IIROULT, OF LA PRAZ, FRANCE, ASSIGNOR TO STEELECTRO METALLURGIQUE FRANCAISE, OF FROGES, ISRE, FRANCE.

ELECTRIC FURNACE.

SPECIFICATION forming part of Letters Patent N o. 721,703, dated March3, 1903.

Application led October 11, 1900. Serial No. 32,667. (No model.)

To a/ZZ whom, t may concern.-

Beit known that I, PAUL LoUIs TOUSSAINT IIROULT, a citizen oftheRepublic of France, residing in La Praz, Savoie, France, have inventedcertain new and useful Improvements in Electric Furnaces, of which thefollowing is a specification.

The improvements to which this invention relates have been devised inorder to obtain Io bythe electric furnace soft metals, such as chromium,manganese, or iron, and generally substances which tend to combine withcarbon. In order to avoid as much as possible all possible introductioninto the material operated on of carbon from the electrodes instead ofthe single are which usually heats an electric furnace, two separatearcs in series are,according to this invention, employedl to playthrough the insulating layer of slag 2o between the metal or the fusedconducting material on the one hand and the two electrodes on the otherhand. In order to insure the distinct formation ot' these two arcs, twoaccessory circuits are arranged, connecting outside the furnace each ofthe two electrodes to the fused material,and in each of these circuitsthere is introduced in shunt a voltmeter, the indications of which serveto constantly verify and regulate the position of 3o both electrodes andto determine whether or` not the furnace is operating properly. Thuseither by hand or by automatic mechanism operated by the twoshunt-currents each electrode can be raised or lowered to determine theare, as desired. The outgoing conductor consists of a rod passingthrough the crucible-wall and projecting outside and inside of the same,so that the portion ofthe rod which is melted is replaced by moltenmaterial which 4o fills up the space and insures good conductivity. Whenalternating currents are ernployed and the electrodes are arranged so asto consume equally, the position of both can be regulated at the sametime by employing a single voltmeter between one of the electrodes andthe metal.

Such is the principle of the invention which is carried out as will bedescribed referring to the accompanying drawings.

Figure l is an elevation, partly sectional,

arranged as described in the first place for use with currents eithercontinuous or alternating. Fig. 2 shows the same furnace adapted solelyto alternating currents.

The Crucible d is made of suitable refractory material-such aslire-brick, magnesia, dolomite, lime, silica, chromite, or the likeandit is inclosed in an iron casing. Such a 'crucible is usually providedwith two tapholes at different levels, the one for running out metal,the other for running out slag or the like. In the crucible is placedthe material to be treated, above which the twol electrodes b b arecarried in sockets c c, having current connections d d and longscrewthreaded rods e e,which pass through nutsff, consisting ot' thebosses of bevel-wheels gg, gearing with pinions h h on spindles t' t',that can be turned by hand-wheels .fr Each of the electrodes and theparts belonging to it are carried by a cantaliver-frame t, which is fromover the furnace. A voltmeterm is introd uced in shunt between eachelectrode and the molten metal, and these show how the operationproceeds, .so that according to these indications the attendant canraise or lower either electrode, so as to regulate each of the arcs.

In Fig. 2 the two electrodes n o are shown to be carried by an insulatedcross-head p, each having its current connection.

A voltmeter r is introduced in a shunt-cir cuit between one of theelectrodes and the molten metal. This indicates variations of tension,so that the distance between the electrodes and the bath of metal can bevaried, as required, by raising or lowering the screwed rod s, whichcarries the electrode and is worked in the same way as was describedwith reference to Fig. l. Obviously such an arrangement could beemployed with triphase or polyphase currents by providing more than twoelectrodes with the means described of regulating their positions.

Y The arrangement of the voltmeter between the electrodes andthe moltenmaterial, while the electrodes themselves are in series with each other,serves to indicate at once and without the necessity of directinspection the occurrence of a short circuit between the electrodes, anoccurrence which would not only hinged at Z, so that it can be turnedaside IOO . duction.

When the arrangement is applied to the manufacture of steel or meltediron, there is directly obtained in the crucible metal decarburized bythe slag, and the reducing gases in passing through the soft ore betweenthe electrodes so act that the ore is partly reduced before undergoingelectrical fusion. Cast-iron can also be decarbureted or dephosphoratedby the use of reagents according to the Thomas process.

The slag which forms the resisting medium in which the heat is producedmay be of various compositions. For example, when the furnace is usedfor the production of metals the slag is mostly imperfectly-reducedmineral matter, or if the furnace be used to obtain stability ofcomposition of mixtures of line steel with other elements-such aschromium, nickel, tungsten, bc-the slag is composed chiefly of reagentsdesigned to act on the bath of metal-such as lime, dolomite, or oxid ofiron liquefied by the addition of silicaor it may be substantiallyneutral, such as a fusible silicate which has no chemical action on thebath.

The voltmeter-terminal which communicates with t-he materialin theCrucible is preferably a rod of the same metal as that being produced inthe Crucible and is built into or passes through the refractory wall ofthe Crucible into the material within the same.

Then the rod melts, the space or hole which it leaves in the wall isilled with molten conducting material, the extent of fusion of which islimited by the proximity of the cold exterior wall. As the currentcarried by this terminal is only a few milliamperes, this arrangementworks very well.

I am aware that there are already in use electric furnaces having twoelectrodes of the Cowles kind; but in these furnaces, which aregenerally inclosed in non-conducting materials, it is only by accidentthat the main arc snbdivides into several partial arcs. This may alsohappen in furnaces in which the arc plays on the treated substance or isblown upon it by a magnet. I am also aware that there are furnaces withmultiple electrodes producing several arcs playingabove the materialtreated and heating by radiation and not by passing through it.

l claim- 'In an electric furnace, the combination of a Crucible adaptedto carry a bath of molten material, two electrodes supported above itand connected in series, a conductor in position to edectcontact withmaterial contained in the crucible and a voltmeter in shunt between oneof said electrodes and said conductor, said conductor consisting of arod passing through the refractory material of the Crucible andprojecting outside and inside of the same whereby the portion of the rodwhich is melted is replaced by molten material which lls up the spaceand thus insures goodconductivity.

ln witness whereof l have hereunto signed my name inthe presence of twosubscribing witnesses.

PAUL LOUIS TOUSSMNT HROULT. Vitnesses:

JULES ARMENGAUD, Jeune, EDWARD P. MAGLEAN.

